Solar Photovoltaic
(PV) Systems

Photovoltaic (PV) solar electricity
systems have captured a lot
of interest as the system components have grown more mature, capable, and
reliable.

The references and articles below
provide PV system basics, examples of the four common types of PV systems used
to
generate electric power, reviews of PV system components, lots on how-to build
your own PV system, and a few interesting
"other" PV systems.

Contrary to popular belief, in most
areas it is perfectly legal and relatively straight forward to do your own PV --
we did...

Be sure to do the
Solar Site Survey to make sure
that your PV panels will have an unobstructed sun for the critical part of
the day. The survey should be done from the location where the PV panels
will be mounted.

There are some very heavily advertised guides for sale on the Internet in
the $50 range that promise that you can make PV panels that will provide
"80%" of your homes power for a couple hundred dollars.

You can be sure that anyone making these kinds of claims is a scammer --
don't waste your money. You will find plenty of free and honest information below
for reputable sources.

Before
you embark on any of the solar projects listed below, you MUST do a solar
site survey.
This will ensure that you actually get enough sun on your collector to make
it worthwhile.
It only takes an hour, its fun, its easy and you will learn something about
how the sun moves.
Solar Site Survey...

This
appears to be a good tool for estimating the economic return for installing
a PV system for your area.
Allows you to change location, size & cost of array, and financing.
Shows details on power output, cost savings, and return on your investment.
While it is offered by a company selling PV equipment, it does not appear
(to me) to be overly optimistic on power generated or savings.

A
good primer on what's involved in planning for an living in an off-grid home
with solar electricity generation.
A lot of emphasis on the conservation steps needed to get demand down.
Not a lot of hands-on, but a very good introduction.

This is a list of discussion forums I like. You can post questions on
these forums and get answers. As always on the Internet, the level of
expertise varies from very high to very very low, so be careful to confirm
the advice you get in some way.

Every once in a while you still find people saying that the energy and
pollution involved in making PV cells exceeds the energy use or pollution
they prevent during their life. This is completely and totally false
-- here is the latest paper verifying this.

Conclusion of the study: "Using data compiled from the original records of twelve
PV manufacturers, we quantified the emissions from the life cycle of four
major commercial photovoltaic technologies and showed that they are
insignificant in comparison to the emissions that they replace when
introduced in average European and U.S. grids."

This is a simple and easy to build solar PV system that will provide some emergency power during power outages, and can also be used for camping or for supplying power to a few things around the house on a routine basis.

This
is a really nice system that fits into a pickup truck. The 320 watts
of PV fit on the existing roof rack, and the 400 amp-hours of batteries in
the side compartments. A pair of
Morningstar charge controllers complete the system.
Great system for camping, tradesmen, RVs, power outage emergencies, ...Full details on the construction and wiring...

This
is another example of putting together a small, standalone PV system on a
shoestring.

Ron's system makes use of inexpensive used PV panels, a kit charge
controller, and low priced sine wave inverter to build a 300 watt system
that he uses to power some loads that are independent of the grid, and also
to provide some backup when the grid power goes out. Its
also a great way to learn about solar electricity without spending a lot of
money.

Small and Simple in the North Woods
Joan R. Surber and Roberta L. Corrigan

Good article on a very small PV system
that can be easily removed and taken along to a new house. 32 W PV panel,
64 AH of battery capacity in a box, and a 1700 W inverter make up the
system. The total cost is $1350.

Interesting article on a “moveable” 300 W
PV system with batteries. Most of this system fits in and on a wood box.
Covers load analysis, component selection, and building and installing the
system. Cost $4K.

A
good write-up on designing, installing, and maintaining a PV system
for an RV. Lots of emphasis on choosing and maintaining the batteries.
While its RV oriented, most of the information is applicable to and small PV
system.
Note that the PV material is in Part 2 of the article.thanks to Mark for suggesting this)

Using Your Golf Cart or Electric Tractor as Emergency Backup Power -- With
your Grid-Tied PV Array for Charging

This
is our scheme for providing power during outages. A few of the panels
on our grid-tie PV array are rewired (much easier than it sounds) to charge
the batteries on our ElecTrak tractor (which could be a golf cart or
similar).
A inverter/charger is used to power key house loads via extension cords from
the ElecTrak.
The nice thing about this scheme is that it cheap to do and it does not
require maintaining a set of batteries that only get used for power outages.

Off Grid PV
Systems
-- Homes powered by these systems are not connected to the utility grid at
all. The systems have PV panels for generation of power, and batteries
to store power for when the sun is not shining. In some cases fossil
fuel powered generators are used to supplement the solar power. As you
can see from the examples below, these systems can range greatly in size,
complexity and price.

Good article about an off grid house PV
system that started very small and grew to a modest 240 W of PV panels,
660AH or battery capacity, and a 1500 W inverter that meets all their
needs. The system cost $3K and avoided a $37K charge from the utility
company to extend the power grid. Maybe you really don't need to use
30KWH per day?

Good article on an off grid system for a
mountain cabin. The system has 960 W of PV panel, 530AH of battery storage,
and a 7KW backup generator, all at a cost of $15K. The owner of the system
covers planning, designing, and installing the system in good detail.

An
article by Jeff Yago on batteries for off-grid solar electric systems.
The article covers battery types, and goes into caring for and maintaining
batteries for a long life.

Batteries are a high ongoing cost for off-grid solar and its very easy to
kill an expensive battery set before its time, so this is good stuff to
know.

Grid Tie PV
Systems Without Battery Backup -- Homes on these "grid-tied" systems are
connected to the utility grid. When the PV panels are producing more
electricity than is being used in the house, the meter runs "backwards", and
the excess power goes into the utility grid. These systems do not have
batteries for storage of electricity. When the utility power fails,
the lights go out in these houses, even if the sun is shining. But,
the significant cost and maintenance issues owning batteries are avoided.

This
is a very detailed account of planning, designing and installing our own new
2150 watt grid-tied PV system.
A lot of detail is provided on the full process, including deciding on type
of system, how big to make it, where to put the panels, solar site survey,
what kind of mounts to use, building the mounts, installing the components,
doing the wiring, and the performance and economics of the system.

The system uses the same Enphase micro-inverter scheme as Guy's system (just
below), so between these two entries there should be enough detail to keep
you busy for quite a while!

Our Elec-Trak Tractor Project

-- Using an Elec-Trak to Power Your House in Power Outages

-- Charging the Elec-Trak from a Grid-Tie PV System just above(this is one way to get around grid-tie systems
going down in power outages -- and have a good way to mow your lawn to boot
:)

Guy
Marsden describes the whole process of selecting, designing and installing
his new grid-tie PV system. Since Guy and friends did the whole
installation, there is a lot of detail.

Guy's system uses the new Enphase micro inverter system in which each PV
panel gets its own inverter. The Enphase system reduces installation
labor, and allows easier future expansion. Guy also provides
real time system output stats.

Guy has done several fine renewable energy and solar projects, and has
detailed tutorials on each one -- a look through his whole website is
very worthwhile.

This
is a very nice and detailed five part blog from Kevin on planning,
permitting, and installing a micro inverter based 3.84KW grid-tie system.
Kevin worked in partnership with a local electrician -- I think this is a
good approach and likely makes for less to learn and a smoother install.
Lots of good detail on the whole process.

Good
Home Power Article on authors attempt to be "Carbon neutral" through
conservation, less fossil fuel, solar active and passive strategies, and a
grid tied PV system. Most of the article details his experiences with
installing a grid tied PV system in Ashland, OR -- a pretty positive
experience all-around.

Good article on an grid tied PV system in
Northern California. The system has 1320W of PV panels and cost $22K before
rebates. The author installed the system, and covers design and
installation of the system. He also provides very detailed performance
records for the system.

Description of a 4KW
grid intertied, batteryless PV system. A full description of the system is
provided including costs. The system was installed by the owner, and some
of the details of the installation an permitting process are described.

This
is a many page post on Northern Arizona Wind & Sun forum. It covers
the installation of an 8.1KW grid-tied PV system.
Lots of detail is provided, and there is some good discussion of the system.

Construction Details for a PV Array at Craters of the Moon Monument

Some
detailed pictures of a large PV array at Craters of the Moon National
Monument. The clean mounting system and simple wiring and equipment
mounting might provide some helpful ideas for your system.

This
is a huge solar electric installation at the Cold Springs Station on Hwy 50
in a very lonely part of the Nevada desert. It is a 30KW grid
tied PV installation that sells excess power to the utility.Some nice construction details in the photos.

With most grid-tied systems, when the grid goes down, the grid-tie PV system also goes down, and you get no power even if the sun is shining.

This new grid-tie inverter from SunnyBoy provides about 1500 watts of back up power when the grid is down and the sun is out. It does not require batteries to do this -- a major plus.

The article Alex Wilson article from the Green Budilding Advisor site provides quite a bit of detail on it...

Grid Tie PV System Kits -- The systems
listed just below are the first offerings of PV systems that are aimed at
homeowner installation. They are small (but expandable), grid-tied
systems that are relatively easy to install. They all use
microinverters (one per PV panel) to simplify the systems and to allow one
to start small, but easily expand.

NOTE: It appears that all three of the pv system kits listed below have been dropped. I would not let this discourage you from doing your own system, as some of the systems are relatively straight forward to put in as a diy project as long as you are willing to invest some learning time. I would look over the first two systems described in the "Grid Tied PV" section on this page -- they provide quite a bit of detail and should allow you to make a decision about whether you want to tackle installing a system yourself. Another option is to do most of the install yourself and get some help on the parts you don't want to tackle.

All the above links are dead -- it looks like Westinghouse has dropped the diy kit PV systems.

Westinghouse
announced the release of solar PV kits for DIY installation. The kit
includes the PV modules, microinverters, parts for roof mounting, and the
other bits needed to complete the system.

It appears that each PV module mounts to the roof independently, and that
the mounting hardware is included. It appears that the microinverters
are integrated with the PV panel. The kits will be offered in 3 sizes:
1 panel, 4 panels, and 20 panels, where each panel is 235 watts. As
with all microinverter based systems, it is easy to expand the sytem.

The Westinghouse Solar website links to the left give more information on
the system. There are some resources for DIYers, and what looks to be
a detailed and well written installation guide. Westinghouse
appears to be pretty serious about this effort.

The Westinghouse sales person told me that the systems can be ordered via
Lowes Hardware, and the the cost for a 4 panel (940 watt) system is about
$2600. This does not include the Enphase EMU monitoring unit, which
many people will want to monitor the system.
The system is based on the Enphase microinverter -- you can get a detailed
understanding of how this system works and goes together by reading the
first two entries in the Grid Tied PV section ...
I would love to hear from anyone who gives this system a try.

This
is a similar microinverter based DIY PV system kit from Clarian. It
was announced some time back, but is not yet available for sale -- hopefully
soon.
This
BuildItSolar Blog entry and the
Clarian
Website give as good a description as I could work out from the limited
material available.

There are likely many more, and any solar retailer who handles the
microinverter systems can put together a similar kit for you.

These
are starter kits that several of the PV retail suppliers have been offering
based on the Enphase microinverter. These systems typically consist of
one PV panel, one Enphase microinveter, and possibly a rack and some other
odds and end.

The systems are basically one panel versions of
my system, and you can get an idea how the work and how they go together
by reading the details on my system and just reducing the number of panels
from 10 to 1.
Calling these systems kits is a bit of a stretch in that they are not likely
to come with a start to finish step by step manual -- you will get a pile of
parts, and its up to you to work out how they go together. This can be
and interesting challenge or a nightmare depending on what you were
expecting.
The kits vary a great deal in how complete they are. The things that
may or may not be included are: a rack or mounting hardware, the Envoy
monitoring unit, connecting wire and breakers.
These systems are not toys and they are not dead ends -- they are fully
functional (if small) PV systems, and they can be expanded seamlessly up to
multi kilowatt systems as your budget allows. I think they are a good
way to go if you want to start small and learn a lot.
Be aware that even on these small systems, you will be working on 240 VAC
house power circuits -- so, do your safety homework.

Power to the People: How to Build a Plug and Play Grid
Tie Solar Array, from the Ken-nect
Blog

This
is a way to do a small, under the radar, grid-tied PV system that uses a
China import grid-tie inverter.

This could make for a cheap system -- some PV modules are available for
about $1 per watt, and the inverter can be found on ebay for about $0.35 a
watt --add a bit for mounts, wire, etc. and you would likely still be under
$2 per watt.

The utility is not going to approve this as a grid-tie system for net
metering, but if its kept small, net metering is not really a factor as your
usage will nearly always be more than the system is producing. While
the inverter includes anti-islanding, it is not UL approved for grid-tie
use.

Grid Tie PV
Systems With Battery Backup -- These homes are connected to the utility
grid, and work in the same way as the "grid-tied" homes above, but they also
have batteries, which allows the lights to stay on when the utility power
goes down. On the negative side, the systems are more expensive, and
the batteries must be carefully maintained.

Note that new inverters that are designed specifically for grid-tied with
battery backup systems have recently come out -- these include:

This is Bob's blog on installing a grid tied with batteries, Unisolar PV
shingle system. It is very detailed and should be very helpful to
anyone considering doing this.
All the details on the design, solar shingle installation, wiring, and
equipment installation are covered in detail. Thank you Bob!

Very good article on planning, designing and
installing a 4.8KW grid-tied PV system with 400AH battery backup, and a 4KW
inverter. The system also includes instrumentation to monitor the
performance of the system. Quite a bit of component and installation
detail.

PV Tracking and Mounts and Soft Concentrators
-- Systems that track the sun or that use reflective surfaces to concentrate
more light on the PV cells make better use of the expensive PV cell
material.

Very
good paper with results on testing a simple scheme that uses one axis
tracking coupled with high acceptance angle V troughs to provide average
daily concentrations around of around 2. Simple aluminum cooling
fins are used to keep cell temperature comparable to non-concentrating
commercial PV panels.(My thanks to Greg for suggesting this)

Mother
Earth News Article, Issue 48, Nov/Dec 1977.
This article provides some how-to information on designing and building
solar array trackers that use canisters of refrigerant to passively track
the sun. This is similar to the very popular ZomeWorks trackers.
Several designs are discussed.
The trackers in the article use Freon -- in a new design you would, of
course, have to substitute a different refrigerant.

Simplified Building Concepts offers several systems that use standard galvanized metal pipe with fittings that allow the pipe to be configured for just about anything, including PV panel mount racks. Looks like a very flexible and easy to use system, and people report that they are willing to help you make your project work.

Some of the articles above that describe
example PV systems have some construction detail, so see these as well.

PV systems have become more straightforward to install as equipment has been
refined over the years -- grid-tie systems in particular have become much
simpler. But, this does not mean its an easy DIY project.
There are serious safety issues that you must fully understand -- even folks
with considerable AC system wiring experience should be very careful to
learn and understand the hazards of working with strings of PV panels that
will produce several hundred volts whenever the sun is on them.
In addition to the safety issues, there are permits and utility companies to
deal with -- some areas may not even allow a home owner to install his/her
own system. So, as always, do your homework!

See the entries in the other sections on "Off
Grid", "Grid Tied", etc. These articles contain lots of detailed
accounts of DIY installations.

This
is a very helpful set of guidelines on PV system equipment, and particularly
on wiring of PV systems.
I found it helpful in both the planning of the details of the component
locations and the wiring, and as a good checklist on what inspectors will be
looking for.
The second link is 168 page presentation with lots of examples and photos.
Probably more detailed than most will need, but lots of examples of common
mistakes.

The
NABCEB offers certifications for installers of PV systems.
Their web site Resources page has much information of interest to people
want to install a system or want to be knowledgeable about what a good
installation should look like.
The "Study Guide for Photovoltaic System Installers" is a good one.
(thanks to Doug for suggesting this)

A Guide to Photovoltaic (PV) System Design and
Installation,
California Energy Commission, June 2001

This
is a very interesting paper showing the use of PV panels as part of a
shade canopy that provides shade for living space that was overheating and
generates solar electricity as well.

The aim of the project was to provide sufficient shading to keep the living
area behind the canopy from overheating, while at the same time not
providing so much shade that the the deck and living area would be too
dark.

The authors found that by selecting a PV module design that lets some light
through and adding some glazed areas above and below the PV modules that
they could get just the right light levels under the canopy.

This
article describes the use of bifacial PV modules for building sun shade
structures that let a controlled amount of light to penetrate the shaded
area and simultanously harvest solar electricity.

Bifacial PV modules convert light coming in to either side of the PV module
into electricity. In contrast to monofacial PV modules they do not
have an opaque layer beneath the silicone cells -- they are semi-transparent
to sunlight. This can make them ideal for shading structures that want
to pass more light into the shaded area that regular opague modules would.

The article provides an overview of using these panels to design sunspaces,
and gives a few nice residential examples.

These
evaporative coolers use low HP 12V fans that can be powered by PV arrays.

Off Grid Refrigeration

Refrigeration is one of the major
electric loads for an off grid home.
Some of the solutions people are using:

Use a modest size Energy Star rated conventional refrigerator.
This approach has a low initial cost, and pretty good energy efficiency.
See the Energy Star link below for for the best ones.
Conventional freezer above and fridge below are the most energy efficient
and make best use of space.

Use one of the brands that specialize in high efficiency fridges for PV
use, such as SunFrost or SunDazer. Less energy use, but higher
initial cost.

Also listed below are some less conventional solutions that use even
less power, and are inexpensive.

Another option is a propane powered fridges. These are very energy
inefficient fridges, and (I think) are best avoided -- but some like them a
lot.(as near as I can tell looking at energy stats from
sellers, propane fridges use about 5 times more energy than energy star
electrics of the same size)

Energy ratings and energy use for appliances.
Energy advice and online audit for homes. Energy star appliances
and homes.
In my view, the Energy Star program could be more aggressive, but its
certainly a good place to start. For example, they have no plans to
require more efficient refrigerators until 2012 at the earliest -- let them
know you would like to see a more aggressive approach.

This article is from the Mt Best -- Australia solar house site:
http://mtbest.net/ A
very interesting solar house with several unique features, and a bit more
info on the chest fridge.

Another approach here... (if this link does not work, try it here on the Wayback Machine...)
Uses added thermal mass and a simple timer switch -- the thermal mass is
intended to allow the fridge and inverter on an off grid site to be turned off
overnight to save the idle inverter load on the batteries.

The thermostat shown on
this page is reported to allow you to use a chest freezer as a refrigerator
with large energy saving:
Beer Fridge Thermostat

This
refrigerator, which is a converted chest type freezer uses only about 0.1
KWH per day. See the article for details. Latest update includes
a design for a low standby power thermostat.
Apparently not all chest freezers are created equal, as some do not report
quite as dramatic an energy saving as Tom reported in his paper -- so if you
are getting a new chest freezer for this, pick an efficient one to start
with.
One person reported 0.3 KWH per day (108KWH/year) on a newer Kenmore freezer
that was EPA rated at 279KWH per year. So, something like a
quarter of a typical, similar size conventional (upright) refrigerator seems
easily achievable.

This
is just a thought. NovaKool (maybe others?) offers a kit for people
who want to make their own fridges. It consists of a compressor,
evaporator, condenser, controls, and pre-charged tubing -- all the guts of a
fridge. It is intended for boat or RV owners who want a built in fridge.
It uses the DanFoss compressor, which is reputed to be efficient.

If you wanted to make a very efficient fridge, this kit would allow you allow
you to build the box with as much insulation as you want, it could be top
opening, and the compressor could be located in an optimal spot. On
just a rough guess from their specs, you might get down to 0.1 KWH per day
for a very well insulated 8 cubic foot fridge. Unfortunately the kit is
not cheap, but this still might pay well for off-grid PV users.
If anyone has tried this (or similar), please let me know how it turned out
--
Gary

Note: I would not try this unless you have a lot of time to
tinker -- I am guessing there is a significant learning curve
attached to getting one of these operating well.

This
fridge uses a well insulated 300 gallon water/ice container that is cooled by
an outdoor finned tube baseboard unit to supply year round refrigeration
with no energy use. No moving parts.

Other interesting projects on
the same site.

Off Grid Appliances

Finding efficient
appliances for off grid can be difficult, since the power draw is very
important, but you still want an appliance that does the job well -- this
section will collect a few appliances that off-grid people favor:

Ray
was looking for a way to dry clothes in the winter for his off-grid home.
He came up with this design that captures heat from a wood burning boiler or
stove chimney so that the only electricity needed for the dryer is motor and
controls. He provides full details for converting an electric clothes
dryer to use heat from burning wood.

"Big Belly" is a trash bin with built in compaction. It is solar
powered and requires no power connection.
The compactor reduces trash volume by up to 8 times -- this reduces the
number of garbage truck pickups, which in turn reduces energy use and GHG
emissions. Big Belly has very carefully designed power
management, and can go for many cloudy days without running out of power.

Description of using Uni-Solar laminated PV bonded to a metal standing seam
roof produces an almost invisible PV installation. Detailed description of
the laminated PV installation and of the PV system

Good
Home Power article. Mark describes the large PV system that runs his
house, as well as keeping his Toyota RAV 4 EV (Electrical Vehicle) charged.
These EV's are no longer offered by Toyota, and after reading the article,
one wonders why?

PV
modules that resemble roof shingles and tend to blend in with the roof.

Electricity From Solar Generated SteamThere is a persistent interest in schemes that use
concentrating solar collectors to make steam, which is then used to drive a
steam engine or steam turbine, which in turn drives an electrical
generator.
One of the advantages of this plan is that solar thermal collectors to make
steam are several times more efficient than PV modules, but this is somewhat
offset by the low efficiency of steam engines.
Just below is all I could find on this area -- if you know of more
information, please let me know.

Note: Even though there is quite a bit of interest in this area, I was not
able to find much on small scale projects -- if you have experience in this
area, or find any interesting material, please let me know.

There
are many examples of successful large commercial electrical generation
plants that use large arrays of parabolic collectors heating fluid at their
focus, or use large fields of heliostats that reflect energy onto a tower
mounted receiver. Some of these plants even include molten salt energy
storage so they can continue to supply power after the sun goes down.

Make Your Own PV Here are some detailed articles on how to build your own
PV panels from individual PV cells.
If you think that you want to roll your own PV panel, these are the best
descriptions I could find -- some of them are very detailed.
Careful weather sealing needs to be addressed.

Caution: bogus books on making your
own PV panels

I've noticed that a number of books have popped up on the Internet and on
ebay that promise to tell you in detail how to easily make PV panels (or
wind turbines).

Many of these are scamsthat contain little or no useful
information. I don't know how you tell the good from the bad, but
the two links below and the ones on the wind page provide quite a bit of
how-to detail for no charge, so I'd start with these.